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NEETPhysicsCurrent Electricity

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Two resistors having equal initial resistance R₀ at a reference temperature, one with a positive temperature coefficient of resistance ( + ) and the other with a negative temperature coefficient ( - ), are connected in parallel. As the temperature of the combination increases, their equivalent resi

Options

  1. ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
  2. BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A)
  3. CAssertion (A) is true but Reason (R) is false
  4. DAssertion (A) is false but Reason (R) is true

Correct answer

D. Assertion (A) is false but Reason (R) is true

Step-by-step solution

Let the resistances at an increased temperature be R₁ = R₀(1 + T) and R₂ = R₀(1 - T) . The sum of the resistances is: R₁ + R₂ = R₀(1 + T) + R₀(1 - T) = 2R₀ This sum is independent of the temperature change. The product of the resistances is: R₁ R₂ = R₀(1 + T) R₀(1 - T) = R₀^2(1 - ^2 T^2) As temperature increases ( T increases), the term (1 - ^2 T^2) decreases, so the product of the resistances decreases. Thus, the Reason (R) is true. The equivalent resistance in parallel is given by: R_ eq = R₁ R₂ R₁ + R₂ = R₀^2(1

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